We propose to purify and chemically characterize the egg development neurosecretory hormone (EDNH) of the mosquito Aedes aegypti. This hormone is released after a blood meal and activates the development of mature eggs. Our current work on this hormone has shown that it is a peptide with a molecular weight of about 6500. We have developed mehods that allow partial purification of EDNH. We propose to continue this work by developing methods for final purification. We propose to determine the amino acid composition and sequence of EDNH if sufficient amounts of pure hormone are obtained. We also propose to investigate the mode of action of the hormone on the ovary, its target tissue. Preliminary evidence implicates cyclic nucleotides but the data are still equivocal. Finally, we propose to determine the nature of the trigger that releases EDNH after a blood meal.